The desire to alter the color of human hair is not a facet of modem times. Since the days of the Roman Empire the color of human hair has been routinely altered to accomodate the changes of fashion and style. However the attainment of precise initial colors which are retained by the hair for a desirable period has remained a more elusive goal. The difficulties in the development of hair coloring compositions which can deliver precise long-lasting colors are in part due to the inherent structure of the hair itself and in part due to the necessary conditions of effective hair coloration processes.
In general, the condition and structure of human hair is not regular along the length of the hair shaft. Human hair is subject to various chemical and mechanical treatments such as combing, brushing, shampooing, heating, perming as well as exposure to the sun. As such, the hair at the ends of the hair shaft will generally exhibit signs of damage relative to the new growth close to the scalp. This damage can lead to inconsistent coloration when the hair is dyed due to irregular uptake of the hair coloring agents along the length of the hair shaft. Thus there is a need for hair coloring compositions which can deliver substantially consistent hair color results throughout the hair.
Once the hair has been colored there is a desire for the color to be resistant to the fading action of the sun and other exterior factors and for the color to be retained in a consistent manner for a predictable period of time. Thus it would be desirable to develop a hair coloring composition which exhibited reduced fade and provided improved resistance to wash out during regular cleansing regimen. An additional difficulty commonly associated with the dyeing of human hair is the need for dye systems which avoid any adverse effect on the hair and skin of the user.
Over the years significant effort has been directed towards the elimination of many of the problems associated with the dyeing of human hair. In particular oxidative dyes have been developed which are small molecules which are capable of diffusing into the hair. As detailed later herein these small molecules may then be activated by a peroxide material and react with further molecules to form a larger colored complex in the hair shaft.
To color human or animal hair using oxidative dye technology it is generally necessary to treat the hair with a mixture of suitable oxidative coloring agents and at least one dye oxidising agent. Hydrogen peroxide is the most commonly used dye oxidising agent. However, in addition to dye oxidation, hydrogen peroxide treatment of the hair can also solubilise the colored melanin component in the hair and can lead to undesirable hair qualities, such as poor condition, due to increased brittleness and hair damage. These undesirable qualities are in part due to the necessary conditions of conventional peroxide treatment, as part of the hair coloring process, which requires high pH (&gt;pH 9), extended exposure (from 10 to 60 minutes) and relatively high concentration of oxidising solutions (up to 20% volume of oxygen) in order to deliver effective dye oxidisation. Thus there is a need for hair coloring compositions which can oxidise dyes and color the hair effectively and also for compositions which can provide desirable hair condition attributes.
Hair coloring compositions containing oxidative dyes, commonly contain, in addition to the dye and a source of peroxide, peroxide activating agents and a variety of additional cosmetic and peroxide stabilising agents. Peroxide dye oxidation agents can oxidise oxidative dyes across a range of pH (pH 2 to 12). However it is known that enhanced dye oxidation can be achieved via the use of a hair swelling agent (HSA) which can adjust the pH of the oxidising solution. Such HSA's further enhance the oxidising and coloring process by swelling the hair fibres to aid both the diffusion of the peroxide and coloring agents into the hair and enabling faster, more thorough dye oxidisation and hair coloring. The preferred HSA for adjusting the pH of peroxide hair oxidising compositions is an aqueous (alkaline) solution containing ammonia (ammonium hydroxide). However ammonia can cause skin irritation when used at levels of about 1% by weight of composition or higher.
Oxidative dyes and peroxide dye oxidising agents can be used to deliver a variety of hair colors to the hair. However such hair coloring compositions comprising oxidative dyes and peroxide dye oxidising agent do not deliver the key consumer needs of color saturation, color vividness, precise initial color predictability, improved wash fastness, improved hair condition and improved safety.
Applicants have now found that the combination of conventional peroxide oxidising agents with certain oxidising aids and one or more oxidative coloring agents in hair coloring compositions can deliver excellent initial hair color, good wash fastness of the hair color over time, desirable color saturation and vividness attributes, and reduced hair damage, are effective at a lower pH and can work in a faster time. Furthermore, applicant has found that the combination of these oxidising aids with a source of peroxide at particular levels and ratios in the coloring compositions of the present invention can deliver these excellent hair coloring attributes results with minimal hair damage at lower pH and in a faster time.
Thus it is an object of the present invention to provide hair coloring compositions which are fast acting.
It is a further object of the present invention to provide hair coloring compositions which deliver improved hair coloring attributes.
It is a still further object of the present invention to provide hair coloring compositions which are effective at lower pH.
It is an additional object of the present invention to provide hair coloring compositions which impart minimal damage to the hair fibres.
All percentages are by weight of the compositions unless specified otherwise.